Use audio frames vs samples consistently in Sonic

In audio processors an audio frame consists of a sample (which is 2 bytes for
16-bit PCM) for each channel. Sonic used "sample" to refer to this.

We've already diverged from the original source for Sonic quite a bit (deleting
code and making stylistic changes) and there haven't been upstream changes so
far, so it seems fine to start making more substantial changes here.

There should be no behavior changes here.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=190916793

library/core/src/main/java/com/google/android/exoplayer2/audio/SonicAudioProcessor.java

@@ -195,7 +195,7 @@ public final class SonicAudioProcessor implements AudioProcessor {
       sonic.queueInput(shortBuffer);
       sonic.queueInput(shortBuffer);
       inputBuffer.position(inputBuffer.position() + inputSize);
       inputBuffer.position(inputBuffer.position() + inputSize);
     }
     }
-    int outputSize = sonic.getSamplesAvailable() * channelCount * 2;
+    int outputSize = sonic.getFramesAvailable() * channelCount * 2;
     if (outputSize > 0) {
     if (outputSize > 0) {
       if (buffer.capacity() < outputSize) {
       if (buffer.capacity() < outputSize) {
         buffer = ByteBuffer.allocateDirect(outputSize).order(ByteOrder.nativeOrder());
         buffer = ByteBuffer.allocateDirect(outputSize).order(ByteOrder.nativeOrder());
@@ -227,7 +227,7 @@ public final class SonicAudioProcessor implements AudioProcessor {
 
 
   @Override
   @Override
   public boolean isEnded() {
   public boolean isEnded() {
-    return inputEnded && (sonic == null || sonic.getSamplesAvailable() == 0);
+    return inputEnded && (sonic == null || sonic.getFramesAvailable() == 0);
   }
   }
 
 
   @Override
   @Override